Point-of-transaction workstations employing laser-based readers and/or imager-based readers have been used in many venues, such as supermarkets, department stores and other kinds of retail settings, as well as libraries and parcel deliveries and other kinds of public settings, as well as factories, warehouses and other kinds of industrial settings, for many years. Such workstations were often configured either as stand-mounted scanners each resting on a countertop and having a presentation window; or as vertical slot scanners each resting on, or built into, the countertop and having a generally vertically arranged, upright presentation window; or as flat-bed or horizontal slot scanners each resting on, or built into, the countertop and having a generally horizontally arranged presentation window; or as bi-optical, dual window scanners each resting on, or built into, the countertop and having both a generally horizontal presentation window supported by a generally horizontal platform and a generally vertically arranged, upright presentation window supported by a generally upright tower. Such workstations were often operated to electro-optically read a plurality of symbol targets, such as one-dimensional symbols, particularly Universal Product Code (UPC) bar code symbols, truncated symbols, stacked symbols, and two-dimensional symbols, as well as non-symbol targets, such as driver's licenses, receipts, signatures, etc., the targets being associated with, or borne by, objects or products to be processed by, e.g., purchased at, the workstations.
A user, such as an operator or a customer, slid or swiped a product associated with, or bearing, the target in a moving direction across and past a respective presentation window in a swipe mode, or momentarily presented, and steadily momentarily held, the target associated with, or borne by, the product to an approximate central region of the respective presentation window in a presentation mode. The products could be moved relative to the respective window in various directions, for example, from right-to-left, or left-to-right, and/or in-and-out, or out-and-in, and/or high-to-low, or low-to-high, or any combination of such directions, or could be positioned either in contact with, or held at a working distance away from, either window during such movement or presentation. The choice depended on the type of the workstation, or on the user's preference, or on the layout of the venue, or on the type of the product and target. Return light returning from the target in the laser-based reader and/or in the imager-based reader was detected to generate an electrical signal indicative of the target. The electrical signal was then processed, and, when the target was a symbol, was decoded, and read, thereby identifying the product.
Early all imager-based, bi-optical workstations required about ten to twelve, or at least six, solid-state imagers having multiple, intersecting fields of view extending through the windows in order to provide a full coverage scan volume in front of the windows to enable reliable reading of the target that could be positioned anywhere on all six sides of a three-dimensional product. To bring the cost of the imager-based workstation down to an acceptable level, it was known to reduce the need for the aforementioned six to twelve imagers down to two imagers, or even one imager, by splitting the field of view of at least one of the imagers into a plurality of subfields of view, each additional subfield serving to replace an additional imager. These subfields also intersected each other in order to again provide a full coverage scan volume that extended above the horizontal window and in front of the upright window as close as possible to a countertop, and sufficiently high above the countertop, and as wide as possible across the width of the countertop. The scan volume projected into space away from the windows and grew in size rapidly in order to cover targets on products that were positioned not only on the windows, but also at working distances therefrom.
Each imager included a one- or two-dimensional, solid-state, charge coupled device (CCD) array, or a complementary metal oxide semiconductor (CMOS) array, of image sensors (also known as pixels), and typically had an associated illuminator or illumination system to illuminate the target with illumination light over an illumination field. Each imager also had an imaging lens assembly for capturing return illumination light reflected and/or scattered from the target, and for projecting the captured return light onto the sensor array. Each imager preferably operated at a frame rate of multiple frames per second, e.g., sixty frames per second. Each field of view, or each subfield, was preferably individually illuminated, and overlapped, by a respective illumination field and extended through the windows over regions of the product. Each imager included either a global or a rolling shutter to help prevent image blur, especially when the targets passed through the scan volume at high speed, e.g., on the order of 100 inches per second.
Preferably, to reduce power consumption, to prolong operational lifetime, and to reduce bright light annoyance to operators and customers, the illumination light was not emitted at all times, but was emitted in response to detection of return infrared (IR) light by an IR-based proximity system that included an IR emitter operative for emitting IR light into an IR emission field, and an IR sensor for sensing the return IR light within an IR detection field. A product entering the IR emission field reflected and/or scattered at least a portion of the emitted IR light incident on the product to the IR sensor. Detection of this return IR light by the IR sensor determined that the product had indeed entered the workstation, thereby triggering the illumination system and the reading of the target.
Although generally satisfactory for their intended purpose, one issue with such known presentation-type workstations involved accidental double-reading of a target, i.e., where a single target was read and reported to a host more than once. If a product with a target was kept in the workstation even after the target was initially read, or if the product was removed too slowly from the workstation, or if the product was moved to different locations in the workstation, a single target might be read and reported several times and, thus, the number of product transactions which were intended to be reported would not correspond to the number of product transactions which were actually reported.
Accidental double-reading was not an issue for handheld scanners that employed a trigger to distinguish among targets. However, the above-described known presentation-type workstations, which were free-running, i.e., triggerless, typically relied on a predetermined timeout period, such as one or two seconds in duration, to prevent accidental double-reads of the same target from being reported to the host. Thus, if a second read, that was identical to a first read, occurred before the timeout period elapsed, then the second read was discarded or not reported, because it was assumed that an accidental double-read had occurred. However, if the second read occurred after the timeout period elapsed, then the second read was reported, because it was assumed that the second read was intentional.
Nevertheless, there were circumstances where it was desired to intentionally read successive identical targets. For example, sometimes multiple identical products from the same supplier, e.g., multiple cans of the same soda brand, were successively swiped or presented at the workstation. Although the known workstations were effective in preventing accidental double-reads by relying on the above-described timeout period, this reliance slowed down any such intentional reading of successive identical targets, because the user had to wait for the timeout period to elapse before the next product could be swiped or presented. As a consequence, the overall throughput of the workstation was decreased, and the performance of the workstation was sometimes regarded as sluggish and, in some cases, was regarded as a defect.
Accordingly, it would be desirable to reliably prevent accidental double-reading of the same target, and to accelerate the intentional reading of successive identical targets without experiencing and being delayed by any fixed timeout period, and to increase the overall throughput of the point-of-transaction workstation.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.